Prevalence of Latent and Active Tuberculosis among Dairy Farm Workers Exposed to Cattle Infected by Mycobacterium bovis

• Published in: PLoS neglected tropical diseases Vol. 7; no. 4; p. e2177
• Main Authors: Torres-Gonzalez, Pedro, Soberanis-Ramos, Orbelin, Martinez-Gamboa, Areli, Chavez-Mazari, Barbara, Barrios-Herrera, Ma Teresa, Torres-Rojas, Martha, Cruz-Hervert, Luis Pablo, Garcia-Garcia, Lourdes, Singh, Mahavir, Gonzalez-Aguirre, Adrian, Ponce de Leon-Garduño, Alfredo, Sifuentes-Osornio, José, Bobadilla-del-Valle, Miriam
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 01.04.2013; Public Library of Science (PLoS)
• Subjects: Adult; Animals; Cattle; Cattle Diseases - microbiology; Cattle Diseases - transmission; Causes of; Disease Transmission, Infectious - statistics & numerical data; Distribution; Female; Humans; Interferon-gamma Release Tests; Latent Tuberculosis; Male; Medicine; Milk; Mycobacterium bovis; Mycobacterium bovis - pathogenicity; Occupational Exposure; Occupational health and safety; Occupational safety; Studies; Tuberculin Test; Tuberculosis; Tuberculosis - epidemiology; Tuberculosis - microbiology; Tuberculosis in cattle; Mycobacterium bovis; Interferon-gamma Release Tests; Humans; Occupational Exposure; Male; Tuberculin Test; Cattle Diseases; Animals; Tuberculosis; Cattle; Adult; Female; Disease Transmission, Infectious; Latent Tuberculosis
• ISSN: 1935-2735; 1935-2727; 1935-2735
• DOI: 10.1371/journal.pntd.0002177

Human tuberculosis caused by M. bovis is a zoonosis presently considered sporadic in developed countries, but remains a poorly studied problem in low and middle resource countries. The disease in humans is mainly attributed to unpasteurized dairy products consumption. However, transmission due to exposure of humans to infected animals has been also recognized. The prevalence of tuberculosis infection and associated risk factors have been insufficiently characterized among dairy farm workers (DFW) exposed in settings with poor control of bovine tuberculosis. Tuberculin skin test (TST) and Interferon-gamma release assay (IGRA) were administered to 311 dairy farm and abattoir workers and their household contacts linked to a dairy production and livestock facility in Mexico. Sputa of individuals with respiratory symptoms and samples from routine cattle necropsies were cultured for M. bovis and resulting spoligotypes were compared. The overall prevalence of latent tuberculosis infection (LTBI) was 76.2% (95% CI, 71.4-80.9%) by TST and 58.5% (95% CI, 53.0-64.0%) by IGRA. Occupational exposure was associated to TST (OR 2.72; 95% CI, 1.31-5.64) and IGRA (OR 2.38; 95% CI, 1.31-4.30) adjusting for relevant variables. Two subjects were diagnosed with pulmonary tuberculosis, both caused by M. bovis. In one case, the spoligotype was identical to a strain isolated from bovines. We documented a high prevalence of latent and pulmonary TB among workers exposed to cattle infected with M. bovis, and increased risk among those occupationally exposed in non-ventilated spaces. Interspecies transmission is frequent and represents an occupational hazard in this setting.